In the field of oceanography and in underwater exploration, there is a need for supporting a payload, such as a transducer, at controlled underwater depths. In some applications, it is desired to control the buoyancy of a submerged vehicle so that the transducer carried by it is moved through a range of depths at a predetermined average vertical velocity. In other applications it may be desired to maintain a transducer at a predetermined depth, within tolerances, for a given period of time.
A particular application of buoyancy control systems is that of controlling the depth of a sonobuoy hydrophone of the type, for example, which is used for detection of submarines. Sonobuoys are typically launched from an aircraft or a ship and upon entering the water, the sonobuoy components are deployed from a casing. A sonobuoy with a hydrophone which is to be operated at a controlled depth may include a buoyant vehicle with a buoyancy control system.
In the prior art, it has been proposed to achieve depth control of such buoyant vehicles by selectively jettisoning a first liquid having a specific gravity greater than the seawater and a second liquid having a specific gravity less than seawater. However, the prior art systems have certain disadvantages in structure and operation.
Sonobuoys, especially those used for submarine detection, are expendable devices and must meet stringent requirements. Such sonobuoys must be of compact structure and must be of low manufacturing cost. In operation, the buoyancy control system must maintain controlled depth for a long period of time with a high degree of accuracy and with the consumption of only a small amount of energy. It should be readily programmable for selected operating depths. It also should operate at low noise to avoid interference with the detection system.
A general object of this invention is to provide an improved buoyancy control system for a submerged buoyant vehicle which overcomes certain disadvantages of the prior art.